The nominal yield stress was measured on centrally perforated plate specimen which was machined from various steels with a wide range of transition temperature measured by V -Charpy test. The load for yielding was determined from the stress-strain curve which was obtained using SR 4 gauge put in touch with the circumference of the hole. The maximum stress at yieding (σ ym ) was calculated from thus measured nominal yielding stress (σ yn ) taking into account the shape factor of the perforated specimen. The values of σ ym , of each steel were evidently higher than their own yield points, and the degrees of rise in σ ym , fairly varied after each steel. Accordingly the existence of notch sensitivity was proved in the phenomenon of yielding of notched specimen about steel. Then the relation was searched between those amounts of rise in σ ym and the transition temperatures, and it was found that the more marked the rise in yielding was, the higher the transition temperature in every steel. The meaning of notch sensitivity in yielding phenomenon was discussed after the stress theory about the yielding of notched specimen set forth by Prof. Ishibashi, and also after the conception of elastic notch sensitivity proposed by H. Neuber. After those theories the relative values of material constant were deduced for each steel as the measure of its notch sensitivity in yielding. Further the literatures were cited to refer the characteristics of similar constant in the study of notched fatigue, taking into consideration the Neuber's conception and presuming the tendency towards brittle fracture of each steel reported. As the result of all-inclusive considerations above, it was denoted that some common factor must have controlled all those notch sensitive phenomena, since there existed similar relations between the material constants of steels deduced from each notch sensitive phenomenon, and close correlations of these constants with the transition temperature.